The utility model discloses an online monitoring device for a cable head in a 10KV switchgear. A 10KV cable head is connected with a Hall current sensor. A cable head grounding line is connected with a control circuit board. An antenna is arranged on the control circuit board. A smoke sensor is connected with the control circuit board. A signal line is connected with the control circuit board and the smoke sensor respectively. A conditioning circuit, a core processing unit and a short message module are successively connected. The online monitoring device breaks through the defects of easy breakdown, high harm, etc. in a prior cable head. A new method is adopted for amplifying leakage current to a linear input range of the Hall sensor and winding an aluminum-packaged grounding line or a grounding line with a metal shielding layer around the Hall current sensor for one thousand circles. The output of the hall sensor is conditioned by the conditioning circuit so that an analog quantity after acquisition of the Hall current sensor is used as input of an AD7656 chip, and the analog quantity is converted to a digital signal and is transmitted to a core processor DSP for processing.